1. Field of the Invention
The present invention relates to differential inductors, and, more particularly, to a differential inductor applicable to asymmetric circuit designs.
2. Description of Related Art
Differential inductors are important passive components in differential amplifiers, and the center-tap kind is a common type of differential inductor.
FIG. 1 is a structural diagram of a center-tap differential inductor 1. Referring to FIG. 1, the center-tap differential inductor 1 has a central conductive wiring 10, a first spiral conductive wiring 11 and a second spiral conductive wiring 12. One end of the first spiral conductive wiring 11 has a first input port 110 and the other end of the first spiral conductive wiring 11 has a contact 111 connected with the central conductive wiring 10. One end of the second spiral conductive wiring 12 has a second input port 120 and the other end of the second conductive wiring 12 has a contact 121 connected with the central conductive wiring 10. Further, the first spiral conductive wiring 11 has a third spanning portion 13 extending across the second spiral conductive wiring 12, and the second spiral conductive wiring 12 has a fourth spanning portion 14 extending across the first spiral conductive wiring 11.
However, the differential inductor 1 is designed to be nearly symmetric and only suitable to be applied in symmetric circuit designs such as specific differential amplifiers or Gilbert mixers. Therefore, in order to design an asymmetric inductor, wherein the inductance values of two inductors are different from each other, two separate inductors are required, thus increasing the overall circuit area. Further, with regards to manufacturing, a large substrate space is required for the circuit layout of a center-tap differential inductor 1, thereby increasing the manufacturing cost.
As a result, it is imperative to provide an asymmetric differential inductor so as to overcome the above-described drawbacks.